Geotextile tubes for protection of mangrove coast at Tanjung Piai Johor National Park, Malaysia

Tanjung Piai Johor National Park is located at the southernmost tip of mainland Asia. It consists of an area of 926 ha, of which 526 ha are mangroves over an 8 km shoreline; part facing the Straits of Malacca and part facing the Tebrau Straits. Mangroves survive in the upper tidal zone, approximately above Mean Sea Level to High Water (Spring). Mangroves exist on gentle sloping coasts with moderate wave climate. A striking feature of mangroves is the root system, which offers protection against erosion of the coast. Matured trees can even withstand an occasional cyclone. The shoreline at Tanjung Piai Johor National Park has been eroding at an alarming rate. Frontlines of matured mangrove trees have been uprooted systematically indicating that the wave climate has exceeded the threshold for a stable and self-sustaining mangrove coast. Detached geotextile tubes mini-breakwaters were conceptualized to moderate incident waves and mitigate further coastal erosion. A pilot project involved the installation of 4 geotextile tubes, each constructed to 1.5 m height and 50 m length was launched in 2003, followed by additional 8 tubes in 2004 and 18 more in 2005 following the success of the earlier installations. The tubes are spaced 5 m apart and aligned parallel to shore. Each tube sits above a scour apron against scouring of the seabed that might undermine the stability of the geotextile tube installed. The installed geotextile tubes are partially exposed during low tides and completely submerged during high tides. Initial observations indicate substrate accretion in the lee of the breakwaters.